Billionaire Carlos Slim speaks during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images

Billionaire Carlos Slim speaks during a news conference with Bill Gates, unseen, to announce donations to Mexico's International Maize and Wheat Improvement Center, known by its Spanish initials as CIMMYT, in Texcoco, Mexico, on Wednesday, Feb. 13, 2013. The group, which performs research for agricultural productivity, will open its research facility this week. Photographer: Susana Gonzalez/Bloomberg via Getty Images